The repair itself went smoothly; the advice to make sure the replacement SSD was properly seated was appropriate.
However, the essential step of transferring the OS from backup was challenging. The replacement SSD (OWC Aura Pro) requires that the computer run High Sierra (macOS 10.13) because of needed firmware, but my computer was running Sierra (macOS 10.12). I installed 10.13 on the SSD that I was about to replace, but this was not sufficient. The replacement SSD was not recognized. The backup from which the system is to be restored also has to run 10.13. I resolved this impasse by booting the computer in target disk mode with a new machine that is running 10.13 and cloning the system from that machine.
The instructions that came with the OWC Aura Pro SSD say, “MacOS 10.13 High Sierra … must be installed on the host computer before installing the OWC Aura Pro SSD.“ This information, along with the fact that the backup must also run High Sierra, should be on this website.
